// Copyright 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_DEBUG_FRAME_RATE_COUNTER_H_
#define CC_DEBUG_FRAME_RATE_COUNTER_H_

#include <stddef.h>

#include <memory>

#include "base/macros.h"
#include "base/time/time.h"
#include "cc/debug/ring_buffer.h"

namespace cc {

// This class maintains a history of timestamps, and provides functionality to
// intelligently compute average frames per second.
class FrameRateCounter {
public:
    static std::unique_ptr<FrameRateCounter> Create(bool has_impl_thread);

    size_t current_frame_number() const { return ring_buffer_.CurrentIndex(); }
    int dropped_frame_count() const { return dropped_frame_count_; }
    size_t time_stamp_history_size() const { return ring_buffer_.BufferSize(); }

    void SaveTimeStamp(base::TimeTicks timestamp, bool software);

    // n = 0 returns the oldest frame interval retained in the history, while n =
    // time_stamp_history_size() - 1 returns the most recent frame interval.
    base::TimeDelta RecentFrameInterval(size_t n) const;

    // This is a heuristic that can be used to ignore frames in a reasonable way.
    // Returns true if the given frame interval is too fast or too slow, based on
    // constant thresholds.
    bool IsBadFrameInterval(
        base::TimeDelta interval_between_consecutive_frames) const;

    void GetMinAndMaxFPS(double* min_fps, double* max_fps) const;
    double GetAverageFPS() const;

    typedef RingBuffer<base::TimeTicks, 136> RingBufferType;
    RingBufferType::Iterator begin() const { return ring_buffer_.Begin(); }
    RingBufferType::Iterator end() const { return ring_buffer_.End(); }

private:
    explicit FrameRateCounter(bool has_impl_thread);

    RingBufferType ring_buffer_;

    bool has_impl_thread_;
    int dropped_frame_count_;

    DISALLOW_COPY_AND_ASSIGN(FrameRateCounter);
};

} // namespace cc

#endif // CC_DEBUG_FRAME_RATE_COUNTER_H_
